This study examined regional cerebral blood flow (RCBF) changes in subjects during worry. The study was conducted in the departments of Psychiatry and Radiology at The Johns Hopkins School of Medicine. It has been completed and was presented at the Society For Neuroscience annual meeting in New Orleans, October 25-30, 1997. An article is under preparation at this time. Following is a description of the methodology and preliminary analysis. Worrying occurs in normals under stress. It also constitutes an important ingredient of pathological anxiety where it occurs in absence of stressors. We examined the effect of worrying on RCBF in 6 right handed normal subjects, physically and mentally healthy and free of drugs (mean age 23 years, range 20-37, 4 female). They underwent 4 sequential PET scans (2 during neutral thoughts, 2 while worrying) using 015-H20 as tracer. Scans of neutral thoughts followed the listening to a 2-minute tape of flower arrangement, worries followed the listening to a 2 minute tape of self-recorded worries (ex. finance, illness in family, work). During scans, subjects continued to think about the topic previously heard on the tape until termination of the scan. RCBF during neutral thinking was compared with RCBF during worrying using MEDx and SPM96. Criteria for significance were: z-score > 3.11(p<.OOI)and at least 25 configuous 2x2x2mm voxels in the cluster. A relative increase in rCBF during worrying was found in the R caudate, R putamen, R inferior frontal gyrus, R inferior parietal lobule, R cerebellar vermis, L posterior cerebellar lobe and R pons. The results indicate right hemisphere and cerebellar activation while worrying. They are congruent with increased R hemisphere EEG activity in anxious individuals and increased RCBF seen in obsessive compulsive patients.